The present invention relates to the art of optics. In particular, the present invention relates to optical spatial filter arrays.
Prior art spatial filter arrays, which are all based on fiber arrays or fiber bundles, include single-mode fiber arrays, photonic crystal fiber arrays, and large mode field diameter (MFD) fiber arrays that are placed inside a single large triangle groove, or 2D array of double-sided micro-fabricated silicon V grooves.
Prior art technologies are based on fiber arrays, which are problematic due to alignment difficulties with the input/output microlens arrays. The assembly and alignment process has been the big stumbling block for the fiber arrays, which makes it difficult to impossible to accomplish the actual fabrication of large arrays. For example, University of Florida fabricated a 42-channel fiber array by placing 42 single-mode fibers in double-sided silicon V-grooves [1. J. Ge, D. et al., “Development of an Extremely Coherent Single Diode Fiber Bundle Array for High Contrast Imaging of Extrasolar Planets with Visible Terrestrial Planet Finder,” SPIE 5491 New Frontiers in Stellar Interferometry, pp. 628-635, 2004.]; Jet Propulsion Laboratory fabricated a 28-channel fiber array by placing 28 large mode fibers inside a triangle area surrounded by three prisms [2. D. T. Liu, et al., “Design and Fabrication of a Coherent Array of Single Mode Optical Fibers for the Nulling Coronagraph,” SPIE Tech Inst for Detect of Exoplanets, pp. 217-228, 2003.]. Fiberguide developed 2D fiber arrays comprising ˜200 single mode fibers, but the 2D fiber arrays have problems to align with microlens arrays. Current fiber array technologies cannot produce 30×30 or larger coherent SFAs.
Visually, referring to FIG. 1, systems developed at NASA's Jet Propulsion Laboratories (JPL) 100 are based upon a triangle gap surrounded by three prisms. About 28 singlemode fibers were placed inside the equilateral triangle area [2. D. T. Liu, et al., “Design and Fabrication of a Coherent Array of Single Mode Optical Fibers for the Nulling Coronagraph,” SPIE Tech Inst. for Detect. of Exoplanets, pp. 217-228, 2003]
And, also visually, referring to FIG. 2, systems developed at the University of Florida and at Penn State University 200 are based upon 2-D array of double-sided micro-fabricated silicon V grooves. Each single-mode fiber was placed in a silicon V-groove [1. J. Ge, D. et al., “Development of an Extremely Coherent Single Diode Fiber Bundle Array for High Contrast Imaging of Extrasolar Planets with Visible Terrestrial Planet Finder,” SPIE 5491 New Frontiers in Stellar Interferometry, pp. 628-635, 2004]